Experimental results about corrosion speed and S-N curve. It'll be possible that we can request the corrosion speed of cable steel under moisture environment through the method of electric chemistry. And it shows the difference clearly. Curving the S-N of cable steel through the effect of corrosive fatigue experiment in 25ﾟC、3%NaCL solution and the fatigue experiment in air, In the case of corrosion, if we make the corrosion speed 15 times faster than the natural corrosion, it will be broken after 2000 million times. In the meantime, its persistence shows 12 percent of which is in air, and 95 percent of the section will be broken.Experiment results about crack growth. The relationship of da/dN-DELTAK about fatigue crack growth will be changed because of different environment. We can also measure the length of crack in corrosion solution by means of current potential method. In order to interpret the phenomenon about the crack opening and closing which is happened in the case of corrosive fatigue, we have been able to make kinds of experiments. And we can show the Kop point clear under experiment so as to put the data in order through the effective stress intensity factor. Using the scanning microscope to observe the broken plane and the length of crack growth and fatigue destruction, we can observe the first crack glinding plane and the striation of the second passage and the wave front of dimple of third passage.